Television system



T. Af SMITH 2,029,395

TELEVISION SYSTEM Feb. 4, 1936.

Filed June ll, 1929 INPI/Flip IL 2 TI INVENTOR T. A. SMH'H ATTORN EYPatented Feb. 4, 1936 PATENT OFFICE TELEVISION SYSTEM Theodore A. Smith,Ridgewood, N. J., assigner to Radio Corporation of America, acorporation of Delaware Application June 11, 1929, Serial No. 369,973

4 Claims.

The present invention relates to television systems, and, moreparticularly, to television systems in which the flicker occurring whentelevision pictures are received is reduced to a minimum extent withoutincreasing the number of pictures received per second.

It is well known in the art to which this invention relates that theintensity of icker occurring when television pictures are projected upona screen so thatthey may be viewed by an observer or an audience is afunction of the intensity with which the screen is illuminated, afunction of the speed at which the screen is illuminated, and a functionof the method and/or order of illuminating the screen.

With these difficulties in mind, it is one of the primary objects of myinvention to provide a system wherein the objectionable flicker may bematerially reduced without increasing the number of complete picturesreceived per second.

Still another object of my invention is to provide a method and means bywhich the same picture in its identical position may be projected uponthe screen two or more times for the purpose of increasing the visualrepresentation of each of the individual points from which eachindividual picture is composed.

Still another .object of my invention is to provide a method and meanswhereby the same identical picture elements maybe projected upon thesame screen at a plurality of time separated intervals, and in the sameidentical position at which they were iirst viewed.

Other objects of my invention are to provide a method and means forprojecting the same image corresponding in intensity to the intensity oflight and shadow on the subject originally transmitted, whether it be amoving subject, a picture subject, a motion picture iilm moving at apredetermined and chosen speed, or any other type of image, which isrelatively simple in its construction and arrangement of parts, aYsystem which is readily adapted to use in connection with the nowexisting types of television receivers Without any substantialmodication thereof, a system which is eicient in its use, convenientlyinstalled, and readily operated.

Other and ancillary objects oi.' my invention will become apparent andat once suggest themselves to those skilled in the art to which theinvention relates by reading the following specication and claims inconnection with the accompanying drawing, wherein:

Fig. 1 thereof illustrates in a schematic manner one form which myinvention may assume ior projecting all of the picture elements twiceupon the same screen at time separated intervals; and,

Fig. 2 illustrates a modification of the arrangement disclosed by Fig. 1wherein high frequency impulses may be projected at one period of timeand low frequency impulses projected at a different period of time inaccordance with the above named objects.

To refer now more particularly to the drawing forming a part .of mydisclosure, the system consists briefly in using a number of glowdischarge lamps which are each operated from the same received signal,but are so connected with properly and appropriately designed delaycircuits that the same electrical impulse applied to the common inputwill cause successive light variations in the lamps. The lamps may be soproperly spaced about the rotating or oscillating scanning element thatthe delayed light falls on a corresponding part of the picture, or, inother words, each lamp is arranged to produce one complete picture foreach rotation of the analyzing disk, but the pictures thus produced areso superposed that, to the eye viewing the television screen, but onesingle picture is apparent.

It will thus be seen that such an arrangement will reduce the flicker toa substantial extent because the picture will be illuminated in a numberof places at once. This illumination will tend to multiply the frequencyof the iiicker by the number of lamps used, and, for example, where twolamps are used, the flicker frequency will be double the iiickerfrequency for a single lamp, and when iive lamps are used, for example,the icker frequency will be ve times the flicker frequency for a singlelamp. It is a well known fact that a higher frequency flicker is not asperceptible to the eye as a lower flicker frequency.

Now referring more particularly to Fig. 1 of the drawing, I haveillustrated, in a conventional manner, a glow lamp I, which is connecteddirectly to an amplifying system 3 connected in turn to a televisionreceiver supplied with energy in accordance with the intensity of lightand shadow over radio, wire, or wired radio systems. In accordance withthe energy derived from the received signals, the lamp I is arranged toproduce a glow of an intensity proportional to the elmental intensitiesof the received picture, assuming the same to be such that for highlight effects on a picture maximum current energy is transmitted, andfor low light effects or dark points on a picture minimum current istransvmitted.

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Still another glow lamp 5 is arranged at a point removed substantially180 from the glow lamp I, and is likewise connected with the amplifyingsystem 3 through a delay circuit generally designated as 'I so that thecorresponding im-V pulses producing a glow in the lamp AEi will bedelayed as regards the time when they reach the lamp Sover the period'of time when they were impressed upon the' lamp I. Suppose, forexample,that the number of complete television pic'- tures received per secondwere n, and it is desired to use two lamps scanning the picture onehalfa picture apart as shown by Fig. 1then the delay circuit 'I must cause alagof seconds for all impulses whichv pass through it.

For the purpose of projecting the image of the glow lamp upon thetelevision screen 9, it is assumedthat a lens oraperture'disk I'Iprovided withlenses or apertures I3positioned in aspiral about theperiphery ofthe disk, in accordance with the teachings of NipkowL isusedfor projecting the light from the lamp upon the screen. It is apparentthat by the use of lensesY I5 and I'I- any light produced in either oftheglow lamps I or 5`-will be projected through the lenses I5 and I1respectively tothe screen 9, and, as shown, the separate light impulsesmay focus at points I Sand 2l, for example. The lens Ii' issocompoundedas to be similar to lens I5, except that it producesjnoreversal of lightdirection passing through it as does I5. Spots I9 and2l will, therefore, move similarly as shown yby the arrows. As shown,lthe impulse or light spot fccused at the'point I9 will be approximatelyonehalfV picture aheadl of the light spot focused at the point 2-Ion-the screen 9, but the spot EI will project the same intensity oflight which had been previously projectedas aspot I 9 at a time one-halfpicture period removed from the time whenthe light spot is focused atthev point 2|.

The disk member I'i may be properly driven and rotated, for example, intheV direction shown by the arrow by any appropriate and desired type ofprime mover which may, in-turn, be synchronized by any knownand desiredtype of synchronizingsystem, for example, by synchronizing impulsestransmitted simultaneouslywiththe television signal, or bytheutilization of synchronizing impulses derived through-the existing powermains suc'h as, for example, 60 cycle A. C. mains. vNow referring toFig. 2 of the'drawing, andv in accordance with the principles,Adisclosed by the schematic and conventional embodiment of Fig. 1 of thedrawing, it will at once 13e-recognized in the use of a delay circuit ofthe type shown conventionally at I'that it may be advisable to pass,only the lower frequencies therethrough and thus apply these lowerfrequencies to the lamp 5. Y It is generally recognized in the art towhich the invention relates that the lower frequencies corresponding toslowly moving objects and objects comparable with the picture size willcause flicker more than the higher frequencies. Thus, an arrangement inwhich all of the received television signals are produced in the lamp Iand only the signals of lower frequency in lamp 5 has been provided.However, such a system may cause certain portions of the picture to be lbrighter than others, and, to avoid repetition of the picture impulses,a high pass filter 25 may be inserted 1n the line connecting' the glowlamp I with the television amplier 3 so as to allow the lamp I toreproduce the high frequency components of the picture, and the lamp 5to produce through the low pass lter 23 and the de#- lay circuit 1, thelower frequency components. In a similar manner, one lamp might producea certain band of the necessary television frequencies, and the otherlamp produce the remainder of the television signalY band. Y

While I have disclosed my present invention as applied to a disk onYwhich there is arranged a Nipkow spiral, which may be either providedwith lenses or apertures,rit is also readily recognized that theinvention is in nowise limited to such a construction but I maysubstitute forV the lens or aperture disk I I a drum disk provided withlenses or apertures Varranged on a helical path, or I may substitute amirror disk or a vibratory member, which isv vibrated in two planes atright anglesto each other, so as to cause the light beam projectedthereon to trace the image in an appropriate manner, or a series Vofydifferent light producing elements successively and cyclically actuatedin any appropriatemanner by received signals, or I may utilizeany otherknown and desired type of scanning or analyzing system without departingfrom the Vspirit and scope of myrinvention, since the invention is notperse directed to any type ofY scanning element only dependently thelight from'said sources through diametrically opposite apertures thereofupon said'screen, and means for controlling the time t of operation ofeach of said sources'so as to illuminate the screen from Veach source'ina'sequential and time-delayed manner, whereby the same intensity oflight is projectedupon said screen a plurality of times attime-separated intervals for each elemental picturearea, and an opticalsystem positioned intermediate one of the light sources andthe screen tocause the scanning path of the resulting light spot to correspond indirection to that of the other scanningpath.

2. In a televisionreceiving system, a scanning element having a seriesof apertures arranged about the periphery thereof, a plurality of lightsources arranged to produce light of an intensity corresponding to theintensity of light and shadow on` individual elements of a picturesurface, a screen, a meansprovided by saidV scanning ele` ment forindependently projecting the intensity of each of said light sourcesfrom diametrically opposite apertures upon the said screen at similarand corresponding points, means for delaying the action of each of saidlight sources with respect Y to the other whereby corresponding pictureintensities are produced in a sequential' and timedelayed manner and anoptical system positioned intermediate one of the light sources and thevscreen to cause the scanning path of the resulting light spot tocorrespond in direction to that of 1 the otherl scanning path. Y

3. In a television receiving system, a rotary Ascanning element, alplurality of light sourcesar- T ranged to produce light of an intensitycorresponding to the intensity of light and shadow on individualelements of a picture surface, a screen, means provided by said scanningelement for independently projecting from diametrically oppositescanning areas thereof the intensity ofeach of said light sources'uponthe said screen at similar and corresponding points thereon, means forproducing a relative time delay in the periods of like illumination ofeach of said light sources with respect to the other, wherebycorresponding picture intensities are produced in a sequential mannerand projected upon said screen a plurality of times and an opticalsystem positioned intermediate one of the light sources and the screento cause the scanning path of the resulting light spot to correspond indirection to that of the other scanning path.

4. In a television system, a screen, a plurality of light sources, meansfor projecting light from said sources upon said screen, means forproducing a portion of the frequencies contained in the electricaltransmission of the television picture from one of said light sources,means for reproducing another portion of the frequencies contained inthe electrical transmission of the television picture from the other ofsaid light sources, and means for delaying the action of one of saidlight sources with respect to the other so as to reproduce saiddiierentfrequencies at time separated intervals.

THEODORE A. SMITH.

